Plate Tectonics Lab 2013-14

1. Plate Tectonics Lab 2013-14

2. 1. Locate the Tonga and Chile areas using the maps on pages 233 682 and 657-657 (map Galoob copied for you). What is subducting in each location? Under which plates are those plates subducting? At the Tonga area: • the Pacific Plate is subducting and the IndoAustrailian Plate is overriding At the Chile area: • the Nazca plate is subducting and the South American plate is overriding

3. 2. Locate the East Pacific Rise on the map on pages 656 and 657.  a. Compare the distance of the Tonga area from the East Pacific Rise with the distance of the Chile area from the East Pacific Rise. • The distance between the Tonga area to the East Pacific Rise is greater than the distance from the Chile area to the East Pacific rise

4. 2. Locate the East Pacific Rise on the map on pages 656 and 657. b. Mid-ocean ridges are the source of oceanic crust. If the East Pacific Rise is the source of the subducting crust in both areas, how do the ages of the two subucting plates compare? • The subducting Pacific plate is older then the subducting Nazca plate. • Because the distance from the East Pacific Rise to the subducting edge of the Pacific plate is further from the mid ocean ridge where the crust was formed.

5. 3. Look at your values in data table B. Compare the focus depth of the majority of the earthquakes at Tonga with those at Chile. 6 26 Most of the earthquakes in the Tonga Area are deep whereas most of the earthquakes that occur at the Chile Area are intermediate.

6. 4. Now look at the profiles you have drawn for the two areas. a. For which area is the subducting plate moving westward? TONGA DATA • In the Tonga area the subducting Pacific plate is moving westward as seen by the earthquakes being shallow in the east and deeper in the west. • In the Chile area the subducting Nazca plate is moving eastward as seen by shallow quakes to the west and deeper earthquakes to the east. WEST CHILE DATA East

7. 4. Now look at the profiles you have drawn for the two areas. b. Which plate is subducting at a steeper angle? • TONGA is subducting at a steeper angle. The earthquakes go from shallow to deep in a shorter distance. TONGA DATA CHILE DATA

8. 4. Now look at the profiles you have drawn for the two areas. c. What does this mean about the type of plate beneath which each plate is being subducted? Explain fully your answer. • The plate at Chile is subducting beneath a continent. The plate at Tonga is subducting beneath an oceanic plate. The subducting plate at Tonga is older and denser therefore it subducts faster and at a steeper angle then the younger less dense crust at the Chile area. TONGA DATA CHILE DATA

9. 5. For the Chile data, the deepest earthquake occurred at longitude 61.7 W and at a depth of 540 km. If the rocks at this location start subducting (left the surface) 10 million years ago and the distance down the subducting plate to the present location is 1000 kilometers, what is the rate of descent, in centimeters per year. Of the subducting plate? Show your work. Given: 1000km in 10,000,000 years. Step 1 convert km to cm 1000 km x 100,000 = 100,000,000 cm Step 2 100,000,000cm ÷ 10,000,000 years = 10cm/year

10. 6. Would you expect the subduction rate at Tonga to be more or less than the Chilean rate? Why? • The subducting plate at Tonga is older, cooler, and more dense so it will dive down at a faster rate then the Nazca plate in the Chile area.

11. 7. Summarize the difference between the subducting plate at Tonga and the subducting plate at Chile by comparing their:

12. 7. Summarize the difference between the subducting plate at Tonga and the subducting plate at Chile by comparing their:

13. How can scientists directly measure tectonic plate movement? GPSMonuments!   The GPS monuments are designed to provide a stable and securely anchored structure, to which the GPS antenna is mounted. Each GPS monument is deeply anchored to ensure high-quality measurements of station positions and velocities. About GPS The Global Positioning System, or GPS, is a global navigation satellite system that provides location and time information anywhere on or near the Earth.  GPS receivers detect signals transmitted by GPS satellites located 20,200 km from the Earth.   An unobstructed view to at least four GPS satellites is required to calculate a GPS position (latitude, longitude, and elevation).   The system can also be used to measure changes in the location of surfaces, horizontally or vertically. http://pbo.unavco.org/instruments/gps

14. Topographical map with labels I’m on top of the Andes mountains

16. Chile Trench example +

17. Earth Quakes Focus or Hypocenter: The point beneath the surface of the earth where the energy is released; point of origin of the earthquake. Epicenter: The point on the earth’s surface directly above the focus of the earthquake. The epicenter is usually where the greatest damage occurs.

18. Tonga Trench (Ocean-Ocean Converging Subducting Boundary)

19. Tonga Area

20. http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=visualizationhttp://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=visualization

21. Chile Trench example + Figure 3